Spatial autocorrelation in biology 1. Methodology |
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Authors: | ROBERT R SOKAL FMLS NEAL L ODEN |
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Institution: | Department of Ecology and Evolution, State University of New York at Stony Brook, Stony Brook, New York 11794, U.S.A.;Department of Ecology and Evolutionary Biology, The University of Michigan, Ann Arbor, Michigan 48109, USA. |
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Abstract: | Spatial autocorrelation analysis tests whether the observed value of a nominal, ordinal, or interval variable at one locality is independent of values of the variable at neighbouring localities. The computation of autocorrelation coefficients for nominal, ordinal, and for interval data is illustrated, together with appropriate significance tests. The method is extended to include the computation of correlograms for spatial autocorrelation. These show the autocorrelation coefficient as a function of distance between pairs of localities being considered, and summarize the patterns of geographic variation exhibited by the response surface of any given variable. Autocorrelation analysis is applied to microgeographic variation of allozyme frequencies in the snail Helix aspersa. Differences in variational patterns in two city blocks are interpreted. The inferences that can be drawn from correlograms are discussed and illustrated with the aid of some artificially generated patterns. Computational formulae, expected values and standard errors are furnished in two appendices. |
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Keywords: | spatial autocorrelation geographic variation analysis spatial variation patterns - Helix aspersa |
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